Does not always start

Have you tried holding the accelerator pedal down 1/4"? If that gets the engine started, there is a very simple relearn procedure you have to do related to low idle speed.

Without punctuation, I'm not sure how to read some of your comments. Please clarify, "several different rebuilds have two that ran when sit a couple of days will not start but has on several tries".

Also, have you checked for spark? Normally crank/no-starts are caused by lack of spark and fuel about 95 percent of the time, so if you're getting fuel, chances are you do have spark and you just need to do the relearn after disconnecting the Engine Computer.

There's about a two percent chance you can have fuel but no spark. We can discuss that if necessary.

I agree with your assessment of unnecessary electronics, but it gets a whole lot worse in later years. That's why my daily driver is a '94 Grand Voyager.

Firing briefly only when releasing the ignition switch is reminiscent of the older vehicles that used that switch to bypass an ignition ballast resistor. That was with the five-pin ignition module, and with breaker points before that. A bypass circuit isn't used with computer ignition systems.

You didn't mention holding the accelerator pedal down 1/4". Did you try that? Chrysler vehicles have an extremely common problem with low idle speed after the battery or Engine Computer is disconnected. That removes memory power from the computer. All of the fuel trim and sensor data will start to be relearned as soon as you start driving, without your even noticing, ... Except for "minimum throttle". Until that is relearned, the engine may not start and run unless you hold the accelerator pedal down 1/4", it won't give you the nice "idle flare-up" to 1500 rpm at start-up, and it will tend to stall at stop signs.

To meet the conditions needed for the relearn to take place, drive at highway speed with the engine warmed up, then coast for at least seven seconds without touching the pedals. We did that as a courtesy on a short test-drive at the dealership, or we instructed the customer on the need to do that. That prevented almost all the complaints after any service that required disconnecting the battery.

You said you have spark, so that rules out a sensor problem. The symptoms you described can be caused by a failed crankshaft position sensor, but then you won't have spark or injector pulses. The Engine Computer has grounded the switched side of the ignition coil to build up its magnetic field, and it is waiting for a signal pulse from the crank sensor to tell it when to turn the ignition coil's ground off so it will make a spark. When no pulse comes from the crank sensor, the only time the computer will turn the ignition coil off is when you turn the ignition switch off. That will create one spark, and that might ignite any fuel that sprayed into the cylinders as a cold-engine priming pulse. That is independent of the normal injector pules timed to the intake strokes.

Wonderful. A lot of people think I'm full of hot air. Well, while that may be true, I do have four Caravans / Voyagers from 1988 through 1995 models, and a '93 Dynasty. Every one of them will have low idle speed after the battery has been disconnected. Sometimes one will start and run without touching the accelerator pedal, but not always.

What the Engine Computer is doing is looking for when your foot is off the accelerator pedal, then it takes a reading from the throttle position sensor and puts that in memory. From then on, any time it sees that signal voltage, it knows it has to be in control of idle speed. At any higher voltage, it knows your foot is on the pedal and it leaves engine speed up to you.

These voltages are approximate, but for explaining theory, the throttle position sensor has mechanical stops that limit its travel to provide a range of signal voltage from 0.5 volt at closed throttle through 4.5 volts at wide-open-throttle. In actual practice you could find closed throttle to be 0.42, 0.57, or even 0.75 volts. The actual value isn't important and will vary between any two sensors. That's why the computer has to relearn that minimum throttle value every time.

That signal voltage will bounce around wildly when you're holding the accelerator pedal down. Since it is possible to hold it perfectly steady, the computer needs some other way to know when your foot is off the pedal. To do that, it wants to see a steady signal voltage along with very high intake manifold vacuum. That high vacuum can only be achieved by closing the throttle right after high opening / high engine speed. The problem is you can achieve that by just snapping the throttle in the garage. To verify you really were driving the vehicle, that high vacuum has to be seen for at least seven seconds. That can't be done in the garage, and is why a test-drive is necessary. Seven seconds is less than half of the typical off-ramp. It may not take that long for the relearn to take place, but the Chrysler instructor told us that would be long enough to cover every vehicle. If you tap any pedal, the computer will abort the relearn procedure and wait for its next opportunity.

Very often competent do-it-yourselfers notice the low idle speed after replacing the battery, and they are smart enough to know some kind of relearn is taking place, but they aren't aware of the need for the test-drive. If the engine won't stay running on its own, less-informed owners may simply give up. It is often necessary to drive with one foot on the accelerator pedal and the other on the brake until you can get on the highway.

I went through a similar situation with one of my minivans. It had a freshly-rebuilt engine, and ran fine, then I let it sit for a year. It took a while to get it started after that. I drove it over 30 miles, then it stalled when I let off the gas on an exit ramp. Wouldn't restart, and had to tow it home. The only thing I can think of is stale gas. I haven't had a problem with gas in two other cars that have been sitting for many years. An 1980 Volare fires right up and runs fine, as does the Dynasty. One is carbureted and one has fuel injection. Both have ten-year-old gas in them. Word in my area is those days are gone, and today's gas won't last. Also, gas formulations vary a lot between different parts of the country, so what works for me might not apply to you.

I forgot to mention earlier that if coasting doesn't restore proper idle speed, use your left foot to hold the brake pedal up while you're doing that procedure. If it vibrates enough, it could cause a momentary pulse in the brake light circuit. That can be enough to abort the relearn.

The last thing is to use a scanner to view live data, and look at the "Idle steps". That will be a number between 0 and 256 while the engine is running. For a properly-running engine, step 32 is typical. With a single-cylinder misfire on a V-8 engine, you'll find it around step 50. If you find it is shown as being on "step 0", that means minimum throttle hasn't been relearned yet.